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MCAT PHYSICS > Lect 5: Fluids & Solids > Flashcards

Lect 5: Fluids & Solids Flashcards

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1
Q

matter that is either liquid or gas; molecules bond weakly, break, and reform because of higher Kinetic Energy; create permanent Forces outward (Normal to the surface); Permanent force withstands the Force parallel to the surface; Matches shape of container; Gravitational Force causes flat top in liquids

A

Fluid

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2
Q

property of fluids that can be externally viewed and measured; Quantity can change
Ex: mass and Energy

A

extensive properties of fluids

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3
Q

properties of fluids that are intrinsic; Independent of quantity;
Ex: density, pressure

A

Intensive

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4
Q

the “heaviness of a fluid”; the mass in a specific volume; changing the amount of the fluid does NOT change this; this is changed only by a change in volume without a change in mass; Solid measurement SI unit = kg / m^3;

A

density (rho)

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5
Q

Equation: Density

A

Density (rho) = m / v

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6
Q

the density of a subject compared to the density of water; ratio quantity

A

specific gravity

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7
Q

If the density (specific gravity) of the substance is less than 1, the substance is _____ than water

A

lighter

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8
Q

if the density (specific gravity) of a substance is greater than 1, the substance is _______ than water

A

heavier

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9
Q

Equation: Specific gravity

A

Specific Gravity = density (substance) / density (water)

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10
Q

Specific gravity / density of water

A

1000 kg / cm^3

1 g / cm^3

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11
Q

a Force per unit area; SI unit = Pascals (Pa)

Note: also “stored” energy per unit area

A

pressure

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12
Q

results from impulse (change in momentum) or F(collision) * time of molecular collisions; change in momentum is the average number of collisions / time of collisions and the surface area of the object in the collisions; SI unit = Pascals (Pa)

A

fluid pressure

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13
Q

Equation: Pressure

A

P = F / A

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14
Q

a fluid at rest only experiences a force ______ to the surface

A

perpendicular

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15
Q

pressure of a disc submerged in water

A

P = weight (m*g) of fluid ABOVE the disc / area of the disc

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16
Q

Pressure is ______ of the area chosen

A

independent

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17
Q

Equation: Pressure of a Fluid at rest in a sealed container w/ uniform density

A

P = (density, rho) * g * y
Note:
y = depth of the fluid
g = gravitational constant

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18
Q

Equation: Pressure of a fluid at rest in an open container

A

P = density (rho) * g * y + P(atm)

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19
Q

Pressure of the atmosphere

A

101,000 Pascals

1 atm

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20
Q

Pressure of a fluid ______ as y (depth of fluid) goes down. Why?

A

decreases; bc there are fewer molecules above the object causing less weight

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21
Q

The pressure compared to local atmospheric pressure;

A

Gauge pressure

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22
Q

“Negative” pressure

A

always refers to gauge pressure; Pressure for the system is less than that in the atmosphere

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23
Q

pressure measured relative to a vacuum as 0

A

absolute pressure

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24
Q

Equation: Absolute pressure

A

P(abs) = P(g) + P(atm)

NOTE: P(g) is Gauge pressure

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25
Q

Each point in an enclosed fluid must bear any increase in pressure
pressure applied anywhere to an enclosed incompressible fluid will be distributed undiminished throughout that fluid

A

Pascal’s Principle

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26
Q

a simple machine that works via Pascal’s Principle; Force on Piston 1 applies pressure on incompressible fluid; All pressure is transferred to Piston 2 (w/ a larger Area)–Force is proportionately greater but acts over a larger distance
So, ∆P1 = ∆P2

A

hydraulic lift

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27
Q

an ideal machine does not change ______

A

Work

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28
Q

the upward force acting on a submerged object;
Displaces volume
due to a difference in pressure
equal to the weight (m*g) of the fluid displaced

A

Buoyant force: F(b)

29
Q

Equation: Buoyant force

A

density (rho) of the fluid * V(g)

Note: V(g) = volume displaced

30
Q

Equation: Floating Object

A

submerged part of the object = density of the object / density of the fluid
Note: If floating in water, the ratio = specific gravity of that object

31
Q

motion in a fluid at rest

contributes to the fluid pressure

A

random translational motion

32
Q

motion that is shared equally by all molecules at a point in the fluid; motion of the fluid as a whole; does not contribute to fluid pressure

A

uniform translational motion

33
Q

Equation: Velocity of fluid coming from a spigot

A

V = √2gh

34
Q

a fluid with no viscosity that is incompressible, no turbulence, irrotational flow

A

ideal fluid

35
Q

measure of a fluid’s resistance to Force that is not perpendicular to the surface; fluid’s tendency to resist flow
Ex: syrup > water

A

viscosity

36
Q

fluid w/ uniform density

*Assume this for MCAT

A

incompressible fluid

37
Q

steady flow of a fluid; all fluid flowes through a fixed point will have the same VELOCITY

A

Laminar flow

38
Q

Equation: Continuity equation (Volume flow rate)

A

Q = A * v

Note: Q = volume flow rate

39
Q

rate at which a volume of liquid moves through a pipe

A

volume flow rate (Q)

40
Q

equals a fluid’s volume flow rate * density

A

mass flow rate (I)

41
Q

Equation: Mass flow rate (I)

A

I = density (rho) * Q = density (rho) * A * v

42
Q

For an Ideal fluid, the ______ is constant, and Area and Volume are ______ related

A 
Flow rate is constant
inversely related (narrow pipe = high velocity)
43
Q

Equation: Bernoulli’s Equation

A

P + density (rho) * g * h + 1/2 * density (rho) * v^2 = K

Note: K = constant specific to a fluid in a given situation of flow; h = distance ABOVE some arbitrary point

44
Q

given one continuous idea flow;
sum of its three terms is a CONSTANT at any point in the fluid
similar to conservation of energy: dividing any term by Volume gives units of energy

A

Bernoulli’s equation

45
Q

Equation: gravitational potential energy per unit volume of a fluid

A

m * g * h / V

Note: Second term in Bernoulli’s equation

46
Q

Equation: kinetic energy from the uniform translational motion of the molecules in a fluid per unit volume

A

(1/2 * m * v^2) / V

Note: third term in Bernoulli’s equation

47
Q

Equation: Energy per volume from the random motion of the molecules in a fluid

A

P / V

Note: First term from Bernoulli’s equation

48
Q

Uniform translational energy borrows energy from _____________. Pressure goes down

A

Random translational kinetic energy

49
Q

Pressure and velocity are ________ related in ideal fluids

A

inversely; As velocity goes down, pressure goes up

50
Q

predicts deviation from ideal fluids; Ex: drag

A

Non-ideal (Real) fluids

51
Q

occurs at the fluid - object interface most often; force is working against the flow

A

drag

52
Q

the intensity of the intermolecular forces per unit length in a fluid
temperature dependent
depends on which type of fluid is interfacing

A

surface tension

53
Q

the force on a fluid causes water droplets by maximizing the surface area

A

intermolecular forces

54
Q

allows a fluid to be pulled up a thin tube

A

capillary action

55
Q

intermolecular force that causes surface tension

A

cohesive force

56
Q

force between molecules of the tube and the fluid molecules

A

adhesive force

57
Q

type of matter in which atoms and molecules are held together rigidly; molecules change dimensions by stretching / compressing but not breaking

A

solids

58
Q

force applied to a solid object / Area over which the Force is acting
i.e. What is done to an object

A

stress

59
Q

Equation: Stress

A

Stress = F / A

SI Unit = N / m^2

60
Q

the fractional change in an object’s shape

i.e. how an object responds

A

strain

61
Q

Equation: Strain

A

strain = ∆dimension / original dimension

62
Q

the maximum stress point an object can take; beyond this point, the object loses its original shape

A

yield point

63
Q

when stress exceeds the yield point for an object

A

Fracture point

64
Q

3 Stress modules for solids

A

young’s module (E) - tensile strength
shear’s module (G) - shear stress
Bulk module (B) - compression / expansion

65
Q

Equation: Young’s module

A

E = (F/A) / (∆h /ho)

66
Q

Equation: Shear’s module

A

G = (F/A) / (∆x / ho)

67
Q

Equation: Bulk module

A

B = ∆P / (∆v / vo)

68
Q

Solids ______ when heated due to more molecular vibrations. May be either linear or volume

A

Expand

69
Q

Equation: Modulus of elasticity

A

Modulus of Elasticity = Stress / Strain

MCAT PHYSICS (5 decks)

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